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The Stokes Raman spectra of pure and hydrogenated amorphous germanium and silicon are discussed. First- and second-order structures due to the vibration of GeGe and SiSi bonds and also first-order structures due to GeH and SiH bonds are observed. The resonance behaviour and the polarization ratio of the observed structures are presented and interpreted in terms of a dielectric constant-bond polarizability model.

The infrared spectrum of hydrogenated a-Ge produced by sputtering in an ArH2 mixture is reported. Bond stretching, bending, and wagging bands are observed. From the integrated absorption of these bands the concentration of GeH and GeH2 bonds is determined. We also report annealing experiments at temperatures below and above that required for crystallization, the amount of this crystallization being determined by Raman scattering. The GeH2 bands disappear upon annealing faster than GeH and virtually none are left in the crystallized material which nevertheless still contains a significant proportion of GeH bonds. The possible structure of the GeH bonds in the crystalline phase is discussed.